Enzymes which utilize lipids as substrates or cofactors possess an extra level of complexity, a lipid-water interface. Several of these enzymes, such as phospholipases, are water-soluble and can utilize non-aggregated lipid, but they require a lipid-water interface for optimal activity. The objective of this proposal is to study this "interfacial activation" of these soluble phospholipases. We propose to isolate and examine three different phospholipases - phospholipase-A2(Naja naja naja), phospholipase-C (Bacillus cereus), and phospholipase-D (cabbage leaf) -and study their interactions with a variety of phospholipid structures. Nuclear magnetic resonance spectroscopy (C-13, P-31, H-1), enzyme kinetics, and chemical modification will be used to examine substrates, substrate analogs, and proteins modified with appropriate reporter groups in order to determine the molecular details and dynamics of phospholipid-protein complexes. It is expected that these studies will contribute to our general understanding of protein-lipid systems.